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首页> 外文期刊>Cement and Concrete Research >A TEM study on the very early crystallization of C-S-H in the presence of polycarboxylate superplasticizers: Transformation from initial C-S-H globules to nanofoils
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A TEM study on the very early crystallization of C-S-H in the presence of polycarboxylate superplasticizers: Transformation from initial C-S-H globules to nanofoils

机译：多羧酸酯超塑料存在下C-S-H的早期结晶的TEM研究：从初始C-S-H球到纳米油的转化

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Polycarboxylate superplasticizers (PCEs) present common admixtures to adjust the rheology of concrete. Previous studies revealed that they can also influence the crystallization of cement hydrates, such as e.g. ettringite. In this study, we investigated the impact of methacrylate ester-based PCEs on the nucleation and crystal growth of C-S-H precipitated from aqueous solutions of Ca(NO3)(2) and Na2SiO3. TEM imaging revealed that in the absence of PCEs following a non-classical nucleation mechanism C-S-H initially precipitates as metastable, globular nanoparticles (droplets, d similar to 20-60 nm) which within less than one hour convert to the characteristic nanofoils of early C-S-H. In the presence of PCEs, the initial globuli exhibit a core-shell morphology, presumably with PCE as shell. The shell was found to delay the conversion to nanofoils for several hours by stabilizing the metastable globules. The PCE polymer exhibiting higher anionicity delayed the conversion to nanofoils more than the PCE possessing fewer carboxylate groups.
机译：聚羧酸盐超塑料（PCE）目前常见的混合物来调整混凝土的流变。以前的研究表明，它们还可以影响水泥水合物的结晶，例如例如，例如， Ettringite。在这项研究中，我们研究了甲基丙烯酸酯基PCS对由Ca（NO 3）（2）（2）和Na2SiO3水溶液中沉淀的C-S-H的核切割和晶体生长的影响。 TEM成像显示，在非典型成核机理的情况下，C-S-H最初沉淀为亚稳态，球状纳米颗粒（液滴，类似于20-60nm），其在不到1小时内转化为早期C-S-H的特征纳米膜。在PCE的存在下，初始球液表现出核心壳形态，大概是用PCE作为壳。发现壳通过稳定亚稳地球将转化为纳米滤体几个小时。表现出更高的阴离子的PCE聚合物比具有较少羧酸盐基团的PCE延迟转化为纳米油的转化率。

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